Glucose-6 phosphate dehydrogenase (G6PD) plays an important role in the regulation of oxidative stress, and its role in vascular disease may be highlighted in blacks with a genetic deficiency in G6PD. The hypothesis of Project 2 is that G6PD takes on importance in providing substrate for the production of superoxide anion (O2-.) by NAD(P)H oxidase in vascular cells activated by cytokines during atherogenesis. Heightened requirements for both increased production of O2-. and nitric oxide (NO.) for both the endothelial and inducible NO. synthases in the atherosclerotic plaque will increase the demand for, and flux of, NADPH, enhancing the importance of G6PD, the rate-limiting enzyme in the pentose shunt that supplies NADPH. We will also investigate the inter- relationship between this proposed pro-oxidant role of G6PD with its anti-oxidant role in providing NADPH for maintaining reduced glutathione (GSH) and protein thiols via GSH reductase and thioredoxin reductase. The specific aims will address the modulation of oxidative stress by G6PD during the development of atherosclerosis. This will be done in Aim 1 by studying the development of atherosclerotic plaques in apolipoprotein deficient mice made deficient also in G6PD. In Aim 2 we will measure the expression of adhesion molecules in cytokine-activated cultured human aortic endothelial cells, a model of the initial steps of atherogenesis that leads to formation of monocyte/macrophage-derived foam cells. In both t he in vivo and in vitro models, we will determine the relative importance of the modulation by G6PD of O2-. production and thiol reduction. In Aim 3, we will examine the role of G6PD in the oxidative stress that may decrease the biological activity of NO. in the vascular smooth muscle of the atherosclerotic mouse and rabbit aorta and in platelets from blacks with G6PD deficiency. This will be done by studying post-translational oxidative modifications in the sarcoplasmic reticulum Ca2+ ATPase, which our group has shown mediates the reduction of intracellular Ca2+ caused by NO. By examining the role of G6PD in modulating oxidative stress in these models of vascular disease, we will ascertain the potential impact and mechanisms by which a deficiency in G6PD may influence atherosclerotic cardiovascular disease in blacks.